According to an epidemiologic study (Scand J Med Sci 1996/ 6: 297-302) the mechanism of "handball goalie's elbow" may be forced hyperextension. The pathomechanics of hyperextension were studied in nine macroscopically normal male cadaver elbow joints. The mean age of the donors was 43.2 years (range 25 to 61 years). Kinematic tests were performed with an experimental three-dimensional kinematic loading apparatus. Hyperextension loads induced joint laxity during flexion of less than 50 degrees. The kinematic changes were significant in joint flexion during forced valgus and external and internal axial rotation, but were not significant in flexion during forced varus. No instability was found with flexion beyond 90 degrees. The hyperextension loads produced four lesions: (1) anterior capsule rupture; (2) L-shaped rupture of the pronator/flexor origin with elongation of the anterior part of the medial collateral ligament; (3) occasional incomplete rupture of the lateral collateral ligament; and (4) small fragments of cartilage near the posterior edge of the ulna in one of the specimens. One or more of these lesions may be responsible for the symptoms in "handball goalie's elbow."